Transition Metal Catalyzed Coupling Reactions Involving Alkynes

Alkynes are important building blocks in modern organic chemistry. They are widely found in nature product, medicines, agrochemicals, functional materials, chemical sensors, fine chemical products, organic intermidiates, etc. Based on this backgroud, this thesis have explored the transition metal catalyzed methodologies of the transition metal catalyzed coupling reactions involving alkynyl groups.Firstly, in Chapter 1, the existance and application of alkynes and diynes in the areas of bioactive nature product, commercially available drugs and functional materials, were introduced, which showed the importance of the alkyne coupling reactions. Later in this charpter, different types of alkyne coupling reactions were briefly reviewed by the classification of the different hybridize status of the coupled carbon atoms, including the history, applications, advantages, limitations and as well as the improvements of them.Then, in the followed several charpters, different types of alkyne coupling reactions were introduced. In Chapter 2, a process of Palladium catalyzed Stille type alkynylation ofα-bromo carbonyl compounds, such as esters and amides was described. In the initial studies, it was found that the concentration of alkynyl tin reagent was crucial to the system. Lower concentration was found to produce higher selectivities and yields. However, the reaction rate, as well as the efficiency was depressed by the decrease of the concentration. Further studies found that ligand may play a more important role in the coupling. Bidentate phosphine ligands were proved to be efficient accelerator to this system, and Xantphos gave the best result. In Chapter 3, the cross coupling between the electrophilic alkynyl bromide and the nucleophilic alkyl Indium reagents in the presence of Pd(dba)2 and CuI were investigated. The P-Olefin Ligand have played key role in this reaction. Chapter 4 have described the synthesis of conjugated diynes through the coupling of alkyne bromide with terminal alkynes catalyzed by Pd(dba)2 and CuI. The P-Olefin Ligand was found to effectively accelerate the reaction rate. Further kinetic experiments have revealed that the reaction rate was zero order to the two substrates. The reaction rate was found to have a linear relation ship to the initial Pd loading, while the initial CuI loading have almost no effect to the reaction rate. A mechanism based on the Sonogashira type coupling was proposed, and the reductive elimination step was proved to be the rate determine step.